1. Field of the Invention
The present invention is related to a steering control system for a moving vehicle, and particularly to a steering control system for various moving vehicles such as mobile machines used for agricultural and civil engineering works, and automatic transporters used in a factory.
2. Description of the Prior Art
A control system is known in which, by causing a moving vehicle to travel in an area for a work (hereinafter referred to as a work area), a predetermined work is done by the working machine equipped on the moving vehicle. In this system, the location of the moving vehicle in the work area is detected and detected positional data is compared with a preset traveling course. Based on the comparison result, the moving vehicle is steered to correct the difference between the current position of the moving vehicle and the traveling course. This control system requires means for detecting the current position of the moving vehicle.
As the means for detecting the current position of a moving vehicle, for instance, there is an apparatus proposed in the Japanese Patent Kokai Publication No. 59-67476 official gazette. This apparatus has means for circularly scanning a light beam around the moving vehicle, and light receiver means. The light beam is projected from the moving vehicle to light reflector means placed at at least three reference positions apart from the moving vehicle. The light reflector means reflect light to the direction of incidence, and the reflected light beam is detected by the light receiver means. Based on the light beam detection signal, the differential azimuths between the respective light reflector means as viewed from the moving vehicle are detected, and the position of the moving vehicle is calculated based on the differential azimuths and the positional information of the light receiver means or the reference points.
However, to make the moving vehicle travel to perform a predetermined work, a traveling course must be first set in a work area. For instance, in the conventional control systems described in Roti et al. U.S. Pat. No. 5,011,288 and the Japanese Patent Kokai Publication No. 2-19293 official gazette, a traveling course is set so that the traveling course comprises a plurality of straight courses which are set perpendicular to the straight line connecting particular to of the plural reference points provided around a work area, and turn courses for moving from one of the straight courses to an adjacent straight course. The control system controls the moving vehicle to travel along the predetermined traveling course. That is, the direction of the straight courses set in the work area is preset by the operator on the basis of the straight line connecting the particular to reference points, and the direction of the moving vehicle is set in conformity with the direction of the preset course.
Also, in the Japanese Patent Kokai Publication No. 64-82206 official gazette, a system for controlling the traveling of an unmanned moving vehicle is described in which the teaching of a work area including reference points is performed or a work start position or traveling course is set each time the work area is changed.
The conventional control systems had the following problems.
The work area in which the moving vehicle travels takes various shapes according to the work to be done, and there are few work area with simple shapes. In the automatic traveling system of this type the traveling extent and traveling course can freely be set or changed according to the size or shape of the work area, and it is required to perform the teaching of the work area including reference points on which the traveling is based, or the setting of a work start position or traveling course each time the work area is changed.
In the control systems described in the above U.S. Pat. No. 5,011,288 and Japanese Patent Kokai Publication No. 2-19293 official gazette, each time the work area is changed, the operator needs to first input the extent, reference points and traveling course, and this is a very cumbersome work.
A proposal for improving such cumbersome work is described, for instance, in the Japanese Patent Kokai Publication No. 64-82206 official gazette, but a portable keyboard input system including a monitor and the like, or a portable handwriting-recognition system is required for teaching. The keyboard input system has a problem that operator training is not easy and not everybody can easily handle it. In the handwriting-recognition system, enough accuracy cannot be obtained if a wide work area is indicated on a small piece of paper or pad, and thus the portable handwriting-recognition system needs very high accuracy. As a result, there is a problem that the traveling control system has a large-scale configuration and it is difficult to automatize the work with a simple operation.
If the system is constructed so that a light beam is rotatively scanned in one direction to detect the reference points in a predetermined sequence, and if a calculation algorithm that sets, on this assumption, a relative traveling course with respect to the individual reference points on a two-dimensional coordinate system is prestored, the sequence of the reference points detection at a work area should coincide with the predetermined sequence. However, the reference point to be detected first (at a smallest azimuth) varies depending on the shape in which the reference points are arranged, and the advance direction of the moving vehicle when the operation of detecting reference points starts. To decide to which reference point in the calculation algorithm which reference point detected at the work side should be assigned, thereby to fulfill the condition that the detection sequence at a work area coincides with the predetermined sequence of the reference points, the operator must confirm the positions of the reference points by eye measurement before the operation starts, and cause the advance direction of the moving vehicle to match the direction that fulfills the above condition. It is very troublesome for the operator to set the moving vehicle in the work area while performing such adjustment for each operation start.